U.S. Pat. No. 3,904,588, granted Sept. 9, 1975, to Greene discloses a continuous process for preparing certain random ethylene/alkyl acrylate/carboxylic acid elastomeric terpolymers which have certain particularly desirable properties. In particular, Greene is directed to elastomeric random terpolymers derived from ethylene, methyl or ethyl acrylate, and an alkyl ester of 1,4-butenedioic acid, which terpolymer possesses exceptional oil resistance and low temperature physical properties that render it particularly suitable for certain industrial applications. The process of the present invention permits preparation of polymers similar to Greene in both composition and properties, particularly bulk viscosity, with a significantly greater throughput, i.e. speed of manufacture, than is possible in preparing the polymers of Greene. In addition, the curing characteristics of the polymers of the present invention and the physical properties of the cured copolymers of the present invention are improved, as compared with Greene's copolymers, when such copolymers are peroxide cured.
Copending U.S. patent application Ser. No. 334,160, filed Dec. 24, 1981 by Nicolas Brodoway, now U.S. Pat. No. 4,399,263, issued Aug. 16, 1983, discloses the modification of elastomeric ethylene/alkyl acrylate/1,4-butenedioic acid ester random terpolymers for the purpose, among others, of increasing the molecular weight (and the bulk viscosity) of such copolymers by reacting the polymer with an amine subsequent to polymerization. For the Brodoway process to be effective, it is necessary for the continuous polymerization to be conducted in such a way as to convert a significant proportion of the carboxylic cure sites to anhydride, which anhydride moiety is capable of reacting with the amine. In contrast, the present invention relates to a process for making ethylene/alkyl acrylate/1,4-butenedioic acid ester random copolymers by co-polymerization of a polyfunctional monomer with ethylene, alkyl acrylate and 1,4-butenedioic acid ester, which process produces a polymer having comparable bulk viscosity much more rapidly than equivalent terpolymer being prepared without polyfunctional monomer, and which resultant polymer has certain other improved properties as described in detail elsewhere in this application.
U.S. Pat. No. 4,065,613, granted Dec. 27, 1977 to Logothetis discloses a batch solution polymerization process of preparing certain ethylene/alkyl acrylate alternating copolymers containing certain branching agents copolymerized therewith, where the branching agent is direactive and may be selected from diacrylates, diolefins and olefin-acrylates. The Logothetis alternating copolymers also optionally contain cure-site monomers, including mono-esters of maleic and fumaric acid. The process of the present invention is continuous, not batch, is based upon a bulk, free-radical polymerization, not a solution polymerization, and produces polymers that are random, not alternating, and do not contain equimolar amounts of ethylene and acrylate.